Don't worry too much about it. You will have so much Dex when you get to level 50, not having that +10 from being a Mathosian is going to make hardly any difference at all. Just stick with the race you like.

Racial abilities once included stat bonuses, but this changed by the time Rift went live. High Elves were given what may be considered the best Guardian racial ability, Angelic Flight. The information you got was simply out of date. So, you should be good to go.

I suspect the racials were changed just so players wouldn't feel they had to roll a certain race for a specific class and if they didn't, they'd feel at a disadvantage. Which I think is a very good thing.